The disclosure relates in general to a spring body for a force transducer or a load cell, particularly for use in the field of process technology, particularly field-device technology, in which an actuating drive moves an actuator, such as a control valve, into a desired position, in order to be able to set a process fluid flow of a processing plant. In particular, the force transducer is integrated as a force coupler in a drive force-transmission structure, such as an actuating-rod structure or actuating-shaft structure, which for example couples an actuating drive, such as a pneumatic actuating drive, to an actuating armature, such as a control valve, of a processing plant for example and transmits the forces from the force generator to the force consumer. The force transducer according to the disclosure can furthermore be used in many fields both of everyday life and in other branches of industry or for research purposes. Force transducers or load cells are generally known as a torque sensor, tension and/or compression force sensor, particularly as a torque sampling cell or tension and/or compression force measuring cell.
In particular, the disclosure relates to a force transducer, in which a torque should be detected, which operates a pivoting movement of a component which is to be set, wherein a pivoting-movement amplitude is limited to less than 360°. Preferably, the maximum rotational-movement amplitude of the actuating drive is limited to 270°, 180°, 120°, 100° or 90° or below. The force transducer can furthermore also be used for any dynamic, rotational-speed-independent measuring tasks, as well as static force measuring tasks.
In the technical field of steering assistance systems, a sensor arrangement for detecting a rotation of a first shaft and a second shaft is known according to DE 10 2010 041 970 A1, in which steering movements of more than 360° are carried out. A torsion rod is coupled in a force-transmitting manner between the mutually separated shafts, which torsion rod transmits the entire force to be transmitted between the two shafts. A retaining device for a magnetic carrier is attached at the facing ends of the shafts. The retaining apparatus is not designed to transmit the actuating forces to be detected between the shafts, but rather is used to amplify a relative movement permitted by the torsion rod between the two facing shaft ends by means of a movement of the magnet carrier. The retaining device is constructed as a web arrangement, which in the case of a rotational movement of the two shafts, permits a translational vertical displacement of the magnet carrier. A sensor apparatus assigned to the magnet carrier detects the change of the magnet field, in order, on the basis of the detected vertical displacement of the magnet, to detect the elastic twisting of the shaft ends permitted by the torsion rod.
A method and a device for detecting static and dynamic torques is known from DE 10 2005 005 715 A1. A rotationally rigid and a rotationally elastic compensation coupling are used. When introducing a torque into the ends of a deformation body of a rotationally elastic compensation coupling, an axial displacement of a central region, which shall be large enough to allow it to be detected using mechanical measuring means, is achieved for an overall length, which is kept constant. The rotationally rigid, but axially elastic compensation coupling compensates the axial displacement permitted by the rotationally elastic compensation coupling again. A washer is mounted by means of a ball bearing at the central region, which washer follows an axial displacement of the central region and remains at a determined circumferential position, in order to be read off by a dial gauge arranged fixed to the housing. The known force transducer is complicated in manufacturing terms due to the multitude of mechanical and kinematic components and it requires a high calibration outlay, in order to obtain precise measurement results. In addition, axial forces which are to be transmitted between the shafts cannot be measured using the known torsional stress meter.
It is known in process technology to detect torques and therefore the measurement of torsional stresses in shafts in a punctiform manner by means of strain gauges, as DE 38 20 838 A1 teaches for example. An electrical resistance within the strain gauge changes because of surface stresses at the point of measurement, which allows conclusions about the torsional load on the actuating shaft forming the surface. The signals at the rotating strain gauge can be forwarded to a position controller by means of induction, radio or a slip ring. This known torque measurement cannot be used in all technical fields of use. The adhesive bonding of the strain gauge is only suitable for certain temperatures. Also, a chemical resistance of the strain-gauge connection is not provided for all surrounding materials. The application of the strain gauge to the deformation carrier is to be carried out with outlay. Wireless transmissions of slip-ring transmissions are not reliable and not permissible in all fields of use, such as in explosive atmospheres, for example in processing plants. In addition, although the measured data are obtained directly at the force-transmitting shaft, they are collected only at a very spatially delimited, punctiform point with regards to the deformation, and therefore are to be considered with a tolerance deduction due to possible material inhomogeneities and must be forwarded by means of energy consumption from the point of measurement of the deformation carrier to a use apparatus.